The Cognitive and Social Neurosciences Lab explores the social, neurophysiological and physical mechanisms of the production of conscious contents in the perceptual, ideational, decisional and motor domains in humans according to their personality traits.

To explore consciousness contents, our subjects are required to go through cognitive tasks built according to experimental psychology principles. During these tasks, visual stimuli are presented on a computer screen and subjects are asked to make a decision while reaction times and brain activity are recorded. In hyperscanning experiments, these tasks are done by two subjects simultaneously.

It is the electrical activity of the brain (EEG) that is recorded for 7 reasons: 1) unlike fMRI, EEG is a direct index of brain computations, 2) EEG follows brain dynamics millisecond by milli-second, 3) valid hypotheses can be made on the brain generators of EEG components, 4) EEG is free from artefacts created, in fMRI, by subtracting the hypo-activities of control conditions, 5) EEG leads to both positive and negative potentials, increasing the odds to differentiate depolari-sations from active inhibitions (hyperpolarizations), 6) unlike magneto-encephalography (MEG), EEG captures scalp-fields whatever their orientation, 7) the cost of hyperscanning with MEG and fMRI is prohibitive.

By isolating all the 1-second-EEG-epochs corresponding to the stimuli of a condition, we compute a mean EEG fragment for that condition. This fragment is made of the so-called event-related brain potentials (ERPs). These are potentials whose latency is fixed relative to the stimulus onset.

We explore the nature of the computations performed by the brain processes responsible for each of these ERPs. From the study of this nature for one ERP, the so-called N400, we built, and now test, a simple theoretical framework. It describes 5 main information processing stages triggered by the presentation of a stimulus: 1) fast, preconscious, bottom-up activations of memorized representtations up to the level of persons (self or others) and contexts representations 2) lateral reciprocal inhibition between competing representations at each level. At the highest level, this competition, which would generate the early part of the N400, would end by the victory of one particular contextual representation, 3) top-down signals coming from that “winner” would further activate all the lower level representations it subsumes, 4) This further activation would induce a surge of the lateral inhibitions exerted by these “subsumed” representations on the competing representations at their level, which would generate the late part of the N400. This surge would make competing representations unable to exert any reciprocal inhibition against winner representations. 5) A tremendous increase of their level of activation would ensue, together with their binding across levels, which would produce conscious contents and generate the positive going ERP that follows N400: the so-called P3b-P600.

Other current activities:

A) We have assembled a bank of names of social roles (e.g., coach) and characterized them along 4 dimensions (favourability, riskiness, ordinariness and arousal). The subject has to decide whether of not he, or another person, would accept playing each role. We are studying why the more subjects are schizotypal the greater the number of extraordinary unfavourable roles they accept.

B) We study the effects of antipsychotic medications on cognition in that task by exploring their impacts on each of the 5 stages of information processing described above. We are trying to understand how these medications prevent inaccurate perceptions (hallucinations), ideas (e.g., delusional beliefs) and why they decrease energy, motivation and affects.

C) We record the ERPs elicited by pronouns in that task (e.g., “me” and “him”) and explore the neurophysiological correlates of the representations of the self and of others.

D) We test whether the binding of the representation of the self with those activated by the stimulus are necessary to conscious perceptions.

E) We also study social cognition and its role in the production of conscious contents. We try to explain why qualia and perceptual worlds can be similar across individuals by testing their non-locality in usual settings, during hyperscanning and (soon) in virtual environments during within-body- and induced out-of-body-experiences.

F) We explore the differences in brain activities observed between participants
who process stimuli together with a closely related person and participants who process stimuli
alone or with a stranger.

During my training in psychiatry, I was interested in the mechanisms of preconscious and conscious identification. I did a PhD thesis on subjects with brain damage having only a precons-cious recognition of the faces of familiar people (prosopagnosics). I did my psychiatric thesis on patients consciously recognizing these faces but denying they are those of such persons (Capgras syndrome). In the 2 cases, I made the hypothesis that an inhibition, indexed by a particular brain potential, the so-called N400, prevented some representations preconsciously activated by faces, to enter the content of working memory.

Invited by Marta Kutas to test this hypothesis that the N400 brain potential is generated by inhibition processes, I showed that words that preconsciously activate more inaccurate representations (like the word "bribe", which also activates the word "bride") and that therefore require more inhibition, evoke greater N400s. I continued to test this inhibition-N400 hypothesis and built a simple framework of the processing of the information conveyed by stimuli (see summary of research). Accordingly, the brain potential following the N400, the P3b-P600, indexes the consciousness of the stimulus and of the meaning of its occurrence in the situation of the experience.

Today, a part of my work focuses on the elementary constituents of consciousness, that is, on qualia. In philosophy, one can consider that they are unique to each individual. But in practice, we always assume that others have similar qualia and that the perceptual world produced by their neurons is similar to ours without taking into consideration the fact that events in consciousness are private.

This assumption of similarity, from which those suffering from mental illness seem to be sometimes excluded, is the basis of the social consensus and of language. However, the origin of this similarity remains mysterious and the radical qualitative difference existing between smells, sounds and colors, for example, contrasts with the resemblance of the neural activities that produce them. The localization of these qualia is also surprising when taking into account the fact that they are produced by the brain. Outside for these three elements, it is internal for emotions, ideas and intentions, except during out-of-body experiences, where these latter sensations are located outside the body. To these experiences, which, today, are induced simply, one can add those of dual conscious presences: the one that is perceived in the avatar in whom we are embodied within the virtual reality displayed and the one that is known to be true, which is the presence in the room where we adjusted the head mounted display in front of our eyes.

This, and other facts, suggest that there may be a physical difference between neuronal activities and the qualia they produce. To test the reality of this difference and the means by which qualia could be similar between individuals, we examine the hypothesis that neurons can produce, in addition to their computational activity, a non-local physical phenomenon that can influence the brain activity of others and have an impact on the qualia they produce. This hypothesis is examined in classical situations and should soon be explored in virtual realities, in collaboration with the Mel Slater, in Barcelona.

If this hypothesis were confirmed, it could have an impact in psychiatry. One could reconsider hallucinations, thought insertions, intentions and the weird feelings reported by psychotic patients as not originating from them. They could be seen as due to a particular sensitivity to these influences, to a deficit of the mechanisms that merge them with their own qualia, to an ability to differentiate these qualia from theirs, or to a deficit of their inhibition. In all these cases, it would be a weapon against the stigma they are subject of, a way to explain their originality relative to others and a track for them to harness their specificities.

Team

Morgan S. White, PhD student

Gifty Asare, MSc student in psychiatry

Maud Haffar, MSc student at the integrated program in neurociences, McGill